1. Field of the Invention
This present invention relates to a substrate holding device in an exposing apparatus for exposing a substrate such as a wafer and an exposing apparatus using the same.
2. Related Background Art
The higher integration of semiconductor integrated circuits has been advanced more and more in recent years, and higher accuracy has been required of an exposing apparatus for making them.
Accordingly, highly accurate positioning is also required of a substrate such as a wafer to be exposed (hereinafter referred to as the "substrate"), and as an example, like the six-axis drive substrate stage described in Japanese Laid-Open Patent Application No. 2-202031, there has been developed a substrate stage of which the movement is adjustable to any position by reciprocal movement along three axes orthogonal to one another and the angles of rotation about respective ones of said three axes are adjustable. A conventional substrate holding device supported on such a substrate stage, as shown in FIGS. 20 and 21 of the accompanying drawings, has a disc-like vacuum clamping plate 106 formed with a groove 106b in the surface thereof for vacuum clamping a substrate (not shown), the vacuum clamping plate 106 being formed with a plurality of holes 106g-106i extending in a direction perpendicular to the surface thereof (hereinafter referred to as the "Z axis direction"), and hollow delivering pins 104a-104c are inserted into the respective holes 106g-106i. The delivering pins 104a-104c are studded in an intermediate plate 103 disposed just beneath the vacuum clamping plate 106, and the intermediate plate 103 supports a plurality of double acting cylinders 105 for moving the vacuum clamping plate 106 back and forth in the Z axis direction.
Also, the intermediate plate 103 is rotatably supported on a base plate 101 by bearings 101a, and is rotated by a drive motor 107 through a worm gear 107a. The base plate 101 has on the upper surface thereof an L-shaped mirror 108 provided integrally therewith, the mirror 108 has mirror surfaces 108a and 108b parallel to two axes orthogonal to each other (hereinafter referred to as the "X axis and Y axis"), and reflects a length measuring laser beam applied to the mirror surfaces 108a and 108b toward a laser interference length measuring machine, not shown. The base plate 101 is formed integrally with a bed plate 102 through resilient hinges 102a, and is reciprocally movable in the Z axis direction or rotatable about the Z axis by an actuator 102b such as an electrostrictive element or a voice coil for fine movement adjustment within a range allowed by the resilient hinges 102a. The bed plate 102 is supported on a conventional six-axis drive substrate stage (not shown).
The delivery and positioning of the substrate (not shown) are effected as follows.
With the double acting cylinders 105 driven to retract the vacuum clamping plate 106, a vacuum clamp force is created in the delivering pins 104a-104c by a vacuum line 104d, and a substrate carried in by a hand (not shown) is adsorbed on the upper ends of the delivering pins 104a-104c. The double acting cylinders 105 are then reversely driven to move the vacuum clamping plate 106 forward, and a vacuum clamp force is created in the groove 106b of the vacuum clamping plate 106 by a vacuum line 106c to thereby adsorb the substrate to the vacuum clamping surface 106a of the sucking plate 106. Thereby, the substrate is firmly held and the flatness thereof is corrected. Further, the positional deviation of the substrate about the Z axis relative to a mask or the like is detected by an alignment scope or the like, not shown, and the motor 107 is driven to rotate the vacuum clamping plate 106, thereby eliminating the aforementioned positional deviation.
An exposing apparatus using a radiation beam of a shorter wavelength has recently been developed, and particularly in an exposing apparatus using charged particle accumulation ring radiation (hereinafter referred to as an "SR-X-ray") as a radiation beam, it is necessary that the substrate in an exposure chamber be held vertically and the exposure chamber be maintained in a reduced pressure atmosphere to prevent the attenuation of the SR-X-ray.
The above-described conventional substrate holding device, however, cannot be used in the exposing apparatus using the SR-X-ray as a radiation beam. The reasons are as follows:
(1) The vacuum clamp force alone created at the upper ends of the delivering pins is insufficient as the vacuum clamp force for effecting the delivery and holding of the vertically held substrate in the pressure-reduced exposure chamber.
(2) In the pressure-reduced exposure chamber, the heat transfer from the substrate to the subatmosphere is small as compared with the atmospheric pressure condition and therefore, the temperature rise of the substrate holding device is remarkable. As a result, positional deviation occurs from the distortion created by the difference in thermal expansion between the base plate and the vacuum clamping plate, and the position of the reflecting surface of the mirror for reflecting the length measuring laser beam fluctuates and a great error occurs to the measurement of the position of the substrate holding device by the laser length measuring machine.
In addition, recently, the substrate is in a tendency toward a larger size and along therewith, a vacuum clamping plate of a large area is required, but a larger size of a mechanism for rotating it is not desirable.
Also, the substrate holding device receives the substrate carried in by the hand and effects the predetermined positioning of it, adsorbs the substrate to the vacuum clamping surface of the vacuum clamping plate and corrects the degree of planarity thereof, and in order that such a correction of the degree of planarity may be effectively effected, the sizes and numbers of the grooves and holes formed in the vacuum clamping surface of the substrate may desirably be small.
Further, to circulate temperature control fluid through the internal piping of the substrate holding device to thereby effectively adjust the temperature of the substrate, it is desirable that the numbers and sizes of grooves and holes for reducing the area of contact between the substrate and the vacuum clamping surface be small. However, if the delivering pins for receiving the substrate carried in by the hand are made too thin or too much reduced in number, a sufficient vacuum clamp force for the delivery of the substrate cannot be created and there will arise a difficulty such as the substrate being inclined during the delivery work or great positional deviation being caused.